Color has long been used to impart a distinctive and aesthetically pleasing appearance to a number of products including toothpastes, coatings, inks and cosmetics. Color is typically provided to such products during the manufacture of the same by admixing in appropriate dyes. Food, Drug and Cosmetic (FD&C) and Drug and Cosmetic (D&C) colors in the United States are water soluble. Accordingly, when such colors are added to products that have a high water content, such as toothpaste formulations, the desired color spreads and uniformly covers the entire product.
Some toothpaste (or other dentifrice) formulations include separate and distinct color components. The colored component can be in the form of speckles that are added to a clear gel or white component to impart a speckled appearance. The colored component could also be in the form of a stripe that is maintained in a discrete layered phase from the white base component. Previous experimentation has shown that the color from water soluble dyes in the colored component of a speckled or striped toothpaste formulation "bleed" into the white or clear gel surrounding component, thereby discoloring the same.
Colorant alternatives to water soluble dyes include pigments. A pigment is generally defined as a finely powdered insoluble material that is dispersed and suspended in the medium to be colored. Pigments are more resistant to color migration when utilized in toothpaste formulations since they consist of water insoluble materials. However, pigments cannot be used in dentifrices in many countries, including the United States, due to safety concerns.
Additional colorant alternatives to the water soluble dyes are "lake pigments." A lake pigment is a term used to define a composition that contains a water-soluble dye and a water-insoluble component to which the dye is chemically bound. The water-insoluble component is typically a metal oxide such as CaO or Al.sub.2 O.sub.3. A drawback associated with existing lake pigments is that, while more color stable than dyes, unacceptable levels of dye migration are exhibited in many applications. For example, a known technique for providing color in a toothpaste formulation is to introduce a lake pigment into a component of a dentifrice formulation. However, color from the lake pigments typically bleed over time and discolor the white component of the dentifrice. This color migration ruins the aesthetic appeal of the dentifrice.
Another technique for providing a striped toothpaste is to physically separate the different colored toothpaste components in different compartments of a toothpaste tube or dispenser. The different colored components do not contact each other until dispensed from the package. Use of this specialized packaging is expensive.